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DCP BlogrollStep By Step: Battlestar Galactica
Feb 1, 2007 12:02 PM, By Ellen Wolff
Forging a Fiery ‘Exodus’
Digital Content Producer's and Millimeter's coverage of past and present award nominees/winners
It’s been 30 years since Star Wars presented dynamic space battles created via painstaking motion control photography. Today, digital tools enable visual effects artists to create intricate, epic battle scenes on a television schedule and budget. A notable example is the Sci Fi Channel series Battlestar Galactica, for which Atmosphere Visual Effects was honored at the Visual Effects Society (VES) Awards this year.
This latest prize was for the "Exodus" episode in season three, which featured a spectacular space battle realized at Atmosphere’s studio in Vancouver, Canada. The sequence includes a vertigo-inducing fall from the sky, and dazzling choreography of missiles and explosions as the spaceship Pegasus is blown apart. It’s a sequence that required exceptional give-and-take between the Atmosphere compositing team led by recent VES winner Brenda Campbell, and the CG team led by Andrew Karr (a VES winner last year for Battlestar.)
Atmosphere, which has worked on the series for three seasons, typically starts each assignment with a previz created in NewTek’s LightWave. For this elaborate sequence, Visual Effects Supervisor Gary Hutzel oversaw the previz directly, explains Karr. “This was done by the Battlestar Galactica inhouse team and then sent to us. That allowed Gary to get faster feedback from the show’s producers. They knew this sequence was going to be huge, so the previz ended up being sophisticated by Battlestar standards. The ships were low geometry, and rendered without textures, yet the previz had gunfire, some particle trails, and roughly comped-in explosions and star backgrounds. But the destruction of the Pegasus and all the pieces breaking apart weren’t in the previz.” Since Atmosphere also uses LightWave, Karr says, “Everyone was on the on the same page. All of the Battlestar spaceship assets are in LightWave.”
While most of the elements in the “Exodus” sequence were digital, there were some practical elements as well. “The sky was painted from actual sky elements [in Adobe Photoshop] and then it was mapped onto a 3D sphere,” Campbell says. “We also added some practical explosions. When they shot the pilot for the show they did a huge pyro shoot. We’ve been reusing those pyro elements ever since.”
The explosions were rendered in several stages within LightWave. “Most of the fire and explosions in the shot were 3D in one form or another,” Karr says. “We had tracking markers so that our compositors could integrate practical elements into the shot.”
The CG spaceships were illuminated interactively with these explosions, and Atmosphere artists also applied interactive lighting to the smoke and missile trails that streak through the sequence. “Most particle work was done in 3D,” Karr explains. “The particles themselves, whether they were sprites or standard LightWave hypervoxels, used practical elements. Small fire elements were mapped onto the particles—kind of half CG and half practical. That’s what ends up giving them the look of real fire, especially with the flak that surrounds the ship like a shield.”
The multi-pass renders of this sequence included an ambient occlusion pass—a cheat for radiosity—simulating diffuse shadows that accentuate the multi-faceted surfaces of the spaceships. This rendering approach enabled the Atmosphere team to change the lighting if necessary without extensive re-rendering.
While Atmosphere benefited from the pyro library, the animations of the ships were created specifically for this sequence. “Other than the models themselves, very little gets re-used from shot to shot or show to show, simply because we don’t ever want anybody to see the same thing twice,” Karr says. “So whenever the spaceships do anything, it’s usually an original animation. In general, this show tends to be extremely low in terms of stock shots.”
Adding to the drama of the “Exodus” sequence is the debris that scatters believably as the Pegasus breaks apart. “From an animation point of view, we were thinking logically about what would blow up first to what would blow up last,” Karr says. “If you simply do something for the sake of looking cool it doesn’t always produce a realistic look.”
The dynamic camerawork that follows the action in this battle is a key aspect of its effectiveness, and Karr notes that Atmosphere was given quite a bit of latitude while creating it. After three seasons of delivering Battlestar Galactica effects, the Atmosphere team knows the drill. “Our supervisor Gary Hutzel always has a pretty clear idea of what he wants to see in a shot. If it doesn’t have that signature Battlestar feel, it doesn’t get approved,” Karr says.
To add to the realism of the sequence, camera shake was added during compositing. Brenda Campbell’s compositing team worked in Digital Fusion, and she says that the flexibility of the software permitted them to finesse the blend of the various elements that comprise the comps. “Getting all the renders broken out and having control in the comp allowed us to have 250 to 350 layers and actually be able to work with them,” she says.
“We’ve gotten into the habit of pre-comping,” Campbell adds. “So, if we have a ship with color correction or a background that we’ve done a lot of extra work on, we’ll process that and then pull it into the comp and add foreground elements.”
While Atmosphere typically turns around a Battlestar Galactica effects assignment in a week-and-a-half to two weeks, Karr says for this particular assignment, the team has six or seven weeks to complete it. What would once have taken months now seems possible in the blink of an eye.
Credit roll
VFX Supervisor - Gary Hutzel
VFX Producer - Michael Gibson
For Atmosphere Visual Effects:
Compositing Supervisor - Tom Archer
CG Supervisor - Andrew Karr
Lead Compositor - Brenda Campbell
Lead CG - Alec McClymont
Compositors - Keegen Douglas, Jeremy Kehler, Nadine Blackler, Jaye Krebs, Tannis Mathers, Mike Porterfield
CG Artists - Paul Hegg, Eric Bates, Chandra Juhasz, Daniel Osaki, Louie Hinayo, Andy Aspirin, Trevor Adams, Scott Paquin, Nik Slotiuk
Matte Painting Lead/VFX Producer - Jeremy Hoey
